"My fourth feeling when I read about [it] was a kind of dread," Whedon told Buzzfeed about Kickstarter. "Because I realised the only thing that would be on everybody's mind right now.

"I've said repeatedly that I would love to make another movie with these guys, and that remains the case. It also remains the case that I'm booked up by Marvel for the next three years, and that I haven't even been able to get Dr Horrible 2 off the ground because of that.

"So I don't even entertain the notion of entertaining the notion of doing this, and won't. Couple years from now, when Nathan [Fillion]'s no longer Castle and I'm no longer the Tom Hagen of the Marvel Universe and making a giant movie, we might look and see where the market is then."